1. Field of the Invention
The present invention relates generally to antennas. Even more specifically, the present invention relates to a system and method for transmitting and/or receiving multiple frequency bands using a single antenna.
2. Discussion of the Related Art
The existing antenna systems used for satellite payloads, aircraft terminals or ground terminals are designed to carry either single or dual frequency band(s) supporting a particular communication service. For example, the Ka-band antennas for Wideband Gapfiller Satellite (WGS) support 20 GHz and 30 GHz frequency bands with less than 40% bandwidth. Future military communication antennas are required to support multiple communication services covering a few or all of the X, K, Ka and EHF bands. This requires an antenna system with about 150% bandwidth and covering more than 6 octaves of frequency bandwidth.
One prior design, as shown in U.S. Pat. No. 6,208,312, issued Mar. 27, 2001, for MULTI-FEED MULTI-BAND ANTENNA, to Gould, which is fully incorporated herein by reference, is an antenna that supports C and Ku band frequencies. The antenna employs a center-fed paraboloid with separate feeds for each band. Each feed covers a narrow bandwidth and the polarization is dual-linear. Another prior design, as shown in U.S. Pat. No. 5,485,167, issued Jan. 16, 1996, for MULTI-FREQUENCY BAND PHASED ARRAY ANTENNA USING MULTIPLE LAYERED DIPOLE ARRAYS, to Wong et al., which is fully incorporated herein by reference, is a multi-frequency band phased array antenna using multiple layered dipole arrays. In this design, each layer is tuned to a difference frequency band and all the layers are stacked together to form frequency selective surfaces. The highest frequency array is on the top of the radiating surface while the lowest frequency array is at the bottom most layer. Disadvantages with this approach are the low antenna efficiency due to increased losses, interactions among layers, high mass and cost associated with phased arrays.
Another version of multi-layered multi-band antenna, as shown in U.S. Pat. No. 6,452,549, issued Sep. 17, 2002, for STACKED MULTI-BAND LOOK-THROUGH ANTENNA, to Lo, which is fully incorporated herein by reference, uses printed dipole elements and slots. In this design, low frequency layer is kept on top of the array while the high frequency layer is kept at the bottom side and both these layers share a common ground-plane at the bottom. It also has similar disadvantages as the multi-frequency band phased array antenna that was mentioned before. Yet another design, as shown in U.S. Pat. No. 5,977,928, issued Nov. 2,1999, for HIGH EFFICIENCY, MULTI-BAND ANTENNA FOR RADIO COMMUNICATION DEVICE, to Ying et al., which is fully incorporated herein by reference, is a multi-band antenna useful for radio communications (AM/FM) by using a multi-band swivel antenna assembly being implemented in coaxial medium. This approach works well over a narrow band and is not suitable at high frequencies. The antenna has very low-gain due to the omni-directional radiation patterns.